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Thread: Come Here And Say That Again - build dairy

  1. #11
    Outlaw's Avatar
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    Daniel Jackson
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    Well I did say some, not all. :B

    Though that second part is a pretty neat idea.

  2. #12
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    Alexander J
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    perhaps you could get 3D printed hubs instead of metal ones? might save a bit of weight and im sure you could knock them up in CAD and get something pretty solid printed

  3. #13
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    Alex Gee
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    Will you be using those dual board VESCs?
    And those motors are 80kV on 5S?

  4. #14
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    In build: Deadlock, Come Here And Say That Again, Now Would Be a Good Time To Panic Retired: Paradig
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    They're nominally 50kv motors (though we measured them as closer to 70kv), running on 10s. Originally it was going to be two of Deadlock's 5s 5Ah packs, but with the weigh issue I'm going to drop down to a more sensible 2.2Ah but still at 10s. I'm using two of these vescs: http://www.ebay.co.uk/itm/VESC-New-4.../182714259982?, which is basically what we have in Deadlock at the moment.
    At 50A it should be able to wheel spin with an opponent on top and have a top speed of ~25mph, but I think the arena's probably a little too small to reach that.
    Does anyone know what size the Robochallenge arena is?

  5. #15
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    Euan Mutch
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    If those are 50kv motors you are going to hit the erpm limit on the vescs

    Edit.. derp I am confusing myself on kv lol it will be fine
    Last edited by TechAUmNu; 16th August 2017 at 12:34.

  6. #16
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    Jamie McHarg
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    Robo Challenge arena is 3.6m x 4.8m if I remember rightly.
    Jamie McHarg
    RogueTwo Robots
    http://www.rogue-two-robots.vze.com

    With great power, comes great reliability.

  7. #17
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    The wedge has arrived, the bends look good but its also heavier than expected. Sigh. The '3mm' Hardox (That I was expecting to be around 3.2mm) is actually 3.4mm. I've looked at the different wheel options and I think I can loose enough weight there for this and the motor mistake, fingers crossed...

    2017-08-16 14.50.32.jpg2017-08-16 15.00.28.jpg

  8. #18
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    mixed progress this week, looking back lots has got done but its not gone that well and its going to be very tight for weight and time. I had a terribly unproductive weekend, making a bunch of mistakes, but the last couple of evenings have gone fairly well.

    The closed cell polyethylene foam for the wheels arrived. The density feels about right to me. fairly stiff but with some give and should save 2kg:
    2017-08-17 11.27.40.jpg
    The lighter batteries also came, they save ~500g:
    2017-08-17 19.13.08.jpg
    I find it amazing that such small batteries can put out so many amps now. Hopefully these can perform to spec. With this change and the foam tyres, I think I'm about on track to be in weight. fingers crossed.

    I've now countersunk the hardox wedge:
    2017-08-20 10.37.34.jpg2017-08-19 20.46.32.jpg

    machined the foam:
    2017-08-22 23.55.13.jpg
    made a lightweight plastic hub:
    2017-08-22 23.57.57.jpg
    trimmed the tread from the kart tyre:
    2017-08-22 23.55.28.jpg
    then stretched the tyre over the foam:
    2017-08-23 00.04.32.jpg
    The wheel's overly complicated but is lightweight and I think will do the job. I expect large chunks will get taken out by any spinners it meets but I think that's probably inevitable with big exposed wheels.

    I've also machined the thick wall aluminium tube axle to take the wheel bearings and eclips:
    2017-08-23 00.06.21.jpg
    It doesn't feel substantial enough for such exposed wheels, but I'm hoping the fact the wheels are foam will limit how much force the axle actually sees.

    Another little thing I'm trying that I thinks fairly new (which I originally wanted to use on Deadlock): a dual removable link with push button quick release pin:
    2017-08-23 00.06.56.jpg
    The sprung balls are locked out unless the button is pushed, so the link is locked in.

    I've also machined the mounts for the wedge rubber
    2017-08-23 00.07.24.jpg

    and machined more dense foam to mount the batteries:
    2017-08-23 00.08.16.jpg
    I rushed this machining, taking much more aggressive cuts than the wheel foam (and forgot to use conventional milling, as that seems to work better on foam), so the finish is really rough but it should do the job.

    The mounting brackets have now arrived, so I tried making a little 3d printed jig to help bend them. it worked perfectly for the first bend but then started cracking and yielding and subsequent bends weren't as good. I need to come up with a better way as I've got another 50 to bend...
    2017-08-22 16.52.57.jpg

    Here's how CHASTA is right now:
    2017-08-23 00.28.59.jpg
    So, getting there. Progress needs to speed up a little if I'm going to be done in time though.

  9. #19
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    Andy Russell
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    Very nice work Mark, look forward to seeing it

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